Andrew Hamilton explains the concept of critical power, and explores recent research on using it for monitoring race fitness and event pacing MORE
Triathlon swimming: do you need to put in the legwork?
John Wood explains why a passive approach to kicking during the swim leg of a triathlon might not be best for triathletes, and provides practical solutions to enhance swimming performance
Because it can be difficult and frustrating to develop an effective kick, the solution for the majority of triathletes has been to simply abandon it. Many triathletes are told to “save their legs” during the swim portion of the race because kicking wastes energy. Indeed, kicking is sometimes seen as counterproductive. This might be partly because previous literature has suggested the primary role of the leg kick is to maintain an optimal body position, stabilise the trunk position and minimise drag1 2 3 4.
A large proportion of triathletes will steer away from any kicking at all because they have poor kicking technique and don’t know how to improve it; rather than seeking help and change, they look to avoid. As a result, many find that they swim quicker with a pull buoy (ie with the legs still) than when they kick their legs. As a coach, I have even seen people travelling backwards as a result of poor leg kick and body position, so it is totally understandable why some might wish to avoid it!
Proactive kicking technique
A good efficient kick can help promote optimal body roll (see figure 1) and rhythm, optimise underwater wrist trajectory (vertical forearm/high elbows), and even help generate more propulsion. I believe that the main role of the leg kick can be any of the aforementioned roles and is dependent on the individual swimmer. Factors such as limb length, body composition, neuromuscular coordination and ankle flexibility can all influence how a swimmer uses their kick, along with the physiological state of conditioning. For example, the use of leg kicking would be limited when the athlete is less comfortable in the water, which could resulting in frantic and knee led kicking.
Figure 1: Body roll5
The kick is also important for the maintenance of momentum during the velocity fluctuations within a stroke cycle. Maintaining momentum within each stroke cycle and between multiple stroke cycles will lead to a more energy-efficient swim, because the swimmer is not constantly wasting energy re-accelerating their body through the water. It is, of course, ideal to also have the stroke timing as optimal as possible. This is so that the leg kick (which requires a substantial portion of the total available energy) does not have to work as hard to maintain velocity by compensating for potential decelerations within the stroke cycle.
Freestyle leg kick is propulsive overall – even if it is not the most efficient (assuming reasonable technique). This means that even if swimmers just kick (no arm movement) at an incredibly slow rate – for example using a 2-beat rhythm using a stroke rate of 30 cycles per minute – the swimmer will still be propelled forward, which shows some extent of propulsion.
In studies carried out to determine metabolic costs of kicking within the swim stroke, swimmers (albeit trained swimmers) were between 10 and 15% quicker while using their legs in conjunction with their arms than they were without kick – regardless of the intensity they were swimming at. Additionally, and possibly surprisingly, there was no higher total metabolic/ energy output6. Clearly this suggests that, provided that the kick technique is sound, having the legs kick at least a little is more beneficial than not kicking.
Indeed, keeping the legs still could actually reduce the efficiency of someone’s stroke; if an athlete has a natural propensity to kick their legs they will be using more energy and concentration keeping their legs taught than by being relaxed. Additionally this may also result in the body sitting lower in the water, and creating more frontal drag, which has to be overcome. More anecdotally, from my own swimming and coaching experience, a good kick can help stretch out tight hip flexors. By stabilising the core through the trunk and kicking both up and down, it can lengthen out muscles that get tight from being sat in day jobs – and also for triathletes who spend hours on the bike closing up the hip joint. Kicking can actually benefit your bike and run.
If an athlete has a natural propensity to kick their legs they will be using more energy and concentration keeping their legs taught than by being relaxed
Best kicking technique
What is the best kicking technique for triathletes – ie one that balances out maximum swim speed with energy efficiency and conservation? First and foremost, each athlete will have their own rhythm – something that suits each individual. Whether they prefer to kick two beat (one kick of each leg to each individual arm pull – ie 1 to 1), four beat (2 to 1) or six beat (3 to1) will come down to feel and preference, and fitting the kick in with their stroke and cadence. That being said, the days of just telling triathletes to kick as little as possible should be numbered!
Freestyle leg kicking should be a full leg movement, from the hip joint down to the toes (see figure 2). Less experienced/ more nervous swimmers tend to kick more from the knee (ie the thigh stays relatively still), which will result in a more dorsiflexed (right angled) ankle. This ankle position can also be seen in people with ankle injuries or with a long running background. Either way, 90 degree ankles are very counterproductive for an efficient kick.
Figure 2: Freestyle leg kick technique
Note the slight knee bend and nicely plantar-flexed ankles (toes in line with shin)
With well conditioned core muscles, it should be relatively easy to have a full up and downward sweep of the leg from the hip joint. The way I like to frame it for swimmers is to think of your leg ‘like a diver’s fin’ – long and flexible, and a smooth arc from hip to toe. For swimmers who bend their knees a lot, a good cue is to try and keep the leg relatively straight. However, there should be a little bit of flex in the knee to allow the top of your foot to face backwards. This is where you want to push water to gain propulsion.
The amplitude of the kick – distance from top to bottom – should be between 8 and 12 inches, and your heels (but not the whole foot) should break the surface. The lower under the water your legs are, the more frontal drag you will encounter and less propulsion you will create. The amount of the force you can produce depends on the surface area pushing backward and the speed or acceleration of that area. Both of those require strong leg muscles and good ankle flexibility.
For swimmers who bend their knees a lot, a good cue is to try and keep the leg relatively straight
Kicking drills to improve technique
When I was swimming competitively, I was a 1500m swimmer swimming 70-80km per week, and I kicked with a 6-beat kick. My coach went by the maxim that 40% of my training on average should be kick training! For triathletes however, a more appropriate rule of thumb is to incorporate 5-10% of your training volume as kicking or kick-based drills. The upside of this is that not only is kicking technique and efficiency improved, but it also helps hone your body position in the water during normal swimming as well. If you are going to incorporate kick training into your sessions, you can split it into the warm up or cool down – it doesn’t have to be in one block.
1. Streamlined kicking – A good kicking drill is ‘streamlined kicking’ on your front (see figure 3). Very rarely do I use a kickboard for practise as it is detrimental to body position and there are no real proven benefits to using them. Focus on bracing your core and keeping your spine long, and if you can bring your arms together in front of you then do. Squeeze your ears between your biceps (dependent on shoulder mobility). Kick along, and when you need to breathe, push your chin forwards, then return to looking down. You can also do this on your back and then breathing isn’t a worry.
Figure 3: Streamlined kick drill
2. Modified streamlined kicking – If you are someone who predominantly kicks from the knee, a modified streamlined kick drill can be of real benefit in helping to reduce this tendency (see figure 4). Rather than having your arms streamlined in front of you, try keeping your arms by your sides and pressing your thumbs into the sides of your glutes (buttock muscles). If your glutes feel like they are working as you kick then you are doing it right! If the muscle feels soft, then your knees are bending excessively and doing too much work. Try it standing up first, kicking one leg to see how it feels. This physical feedback can make a big difference to your technique. It can also aid keeping your ankles plantar-flexed.
Figure 4: Streamlined kick drill with arms by side
3. Side kicking – Side kicking is a good way of nailing body position and a balanced kick at the same time (see figure 5). It forces you to kick up and down – or in this orientation forwards and backwards. Try this:
- Swim with your right arm extended, 3-4 inches below the water.
- Keep your left arm by your side, and twist your body from your hips to face your left hand side.
- Ensure that your hand is pointing where you want to go – it’s acting as your rudder.
Figure 5: Sidekick drill
My preference is to look down, as it helps keep the hips high; then all you need to do is turn your head/neck to breathe. If you find yourself drifting one way or the other focus on making sure that your kick is equally strong in both directions. For instance, if you drift towards your front, kick harder forwards. If you are drifting towards your rear, make sure that your hamstrings are working and kick back harder.
4 – Fins and snorkel kicking – Kicking with fins and/or a snorkel can be beneficial to focus on smooth kicking and getting used to lengthening the ankles whilst not having to worry about breathing (see figure 6). Try switching between having fins on and taking them off to improve your ankle flexibility and mobility.
To start playing around with rhythm and the amount that you kick within your stroke, you can do six kicks to one pull or six kicks to three pulls (some swimmers may know this as 6-1-6 or 6-3-6). Start in the side-kicking position from above, and do six kicks, then take one stroke and roll on to the other side. To do six kicks to three pulls, take three normal full strokes between sets of six kicks.
Figure 6: Fins/snorkel kicking drill
Other conditioning techniques
Ankle mobility is something that can be real limiter to the output of your kick, so it’s good to work on that. A beneficial side effect will be better ‘ankling’ motion on the bike. You can work on this with basic ankle circling, sitting back on your ankles (maybe in front of the TV for a few seconds at a time at the end of the day), or PNF (resisted) stretching.
From a strengthening point of view, any exercise that strengthens your quads (frontal things), hip flexors, glutes and hamstrings (rear things) will have real benefits. Squats and deadlifts will improve your general power – and have obvious transfer over to bike and run as well. Single leg variations like lunges, Bulgarian split squats and single leg deadlifts will have equal benefits, especially given that freestyle kick (and cycling and running) are very much ‘one leg at a time’ activites. A combination of single and double-leg exercises will help improve power and strength through the hip area, but also the stability of the alternating leg actions.
CASE STUDY: Tom Cooling
Tom Cooling is a triathlete that I have worked with. Tom has a super strong bike (sub-6 hours at IM Nice and Wales) and run, but has a relatively poor swim – around 1hr.10mins for both when the fastest athletes are leaving the water in around 50 minutes. Having looked at Tom in the endless pool, we determined that there were two main issues – firstly that his hips were low because of poor head positioning and core control, which meant he was dragging against a lot of resistance. Secondly, his leg kick was nonexistent, primarily because he’d tried to minimise it. Being a runner, his ankles were also quite rigid and fixed, so we had to work around that also.
Tom went away with some of the drills above and worked on both his body position and more importantly his kick, doing some leg work in every pool session and getting away from his reliance on his pull buoy. The progress has been marked. In January (when I first saw him), he was swimming comfortable sets of 10 x 100m at around 1min.50secs/100m. Now he’s swimming sets of 20 x 100m at between 1min.35secs and 1min.40secs/100m – not only around 10% quicker but swimming easier and longer too.
Tom’s main goal this year is to race well at l’Alpe d’Huez triathlon in July, and to be out of the water in less than 33 minutes for the 2.2km swim – which works out at 1.30/100m. I believe that he’s well on the way to doing that, in large part down to improving his kick.
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- Eur J of Appl Physiol, 2016;116(5):1075-1085. DOI: 10.1007/s00421-016-3372-4